When human skin is exposed to a laser beam under the skin temperature of 36 centigrade, on the skin caused is a certain vital reaction, which is called “non-thermal reaction”. It includes photoelectric effect, photo-magneto effect, photo-dynamics effect, photochemical effect, photo-immunization effect, photo-zymogenesis effect and other such like optical effects.
Such non-thermal reactions are applied to body treatments such as slimming and hair restoration, since they stimulate blood circulation, body metabolism and the likes.
Also, when the skin is exposed to a laser beam, Joule heat is caused in the skin tissue by photothermal reaction to raise the temperature of the skin tissue.
The rise of the skin temperature causes various reactions such as; flashing, protein transformation, blood clot, vaporization, and carbonisation.
Such photothermal reactions are applied to beauty treatments such as: a skin beauty treatment, in which birth marks, stains, freckles and other unpleasing pigment cells are reduced into minute particles almost unnoticeable; and a depilation treatment, in which protein transformation is caused in hair root cells to destroy the regeneration mechanism of human hair.
These non-thermal and photothermal reactions can be selectively caused, depending on how much energy density a used laser beam has.
Referring to FIG. 7, a semiconductor laser diode is responsive to application of voltage for starting an electric current to flow, and at the outset it radiates natural light. A laser oscillation is caused when the so started electric current rises beyond a certain threshold value, and the laser output drastically increases in proportion to the increasing electric current, and accordingly the energy density of the laser beam increases.
The object of the present invention is to provide a laser beam irradiation device capable of giving both the non-thermal and photothermal treatments by controlling the amount of electric current excited in its semiconductor laser diode to adjust output power of the laser beam.